html body{
	
	width:900px;
	margin: 0 100px;
	background-color: gray;
	
}




html footer{
	
	text-align:center;
	
}

#caja{
	background-color: #72B4D1;
}

.modal{
	
	display:none;
	
}


.modal_visible{
	
	background-color:red;
	display:block;
	position:absolute;
	width: 71%;
	height: 400px;
	left:center;
	top: 10%;
	
}


.dark{
	background-color: #000;
	opacity:0.18;
}